1. Field of the Invention
The present invention relates to a photograph developing apparatus equipped with a sub-tank. More particularly, the present invention relates to the structure of the lid portion of the sub-tank.
2. Description of the Related Art
There are many kinds of automatic photographic printers such as a large-type photographic printer that can perform processing at high speed and a small-type photographic printer that can be installed in a retail shop or the like. Developing apparatus used in these printers have been improved to operate at higher speed, and photographic materials have progressed as well. In addition, developing temperature has been increased in order to accelerate chemical reaction. Especially, in development of a color photograph, the temperature of processing solution is set higher than in the case of a monochrome photograph.
Although development at high temperature is good in terms of processing speed, resultant enrichment of processing solution concentration due to evaporation causes difficulty in maintenance of the processing solution, such as management of processing solution concentration. If the concentration of the processing solution changes, the processing time and other processing conditions change. Therefore, there has been performed an operation for replenishing water at intervals in order to maintain the processing solution at constant concentration.
Recently, in consideration of cost and environmental problems, there has been developed a developing apparatus that performs development through use of a greatly reduced amount of processing solution. However, when the amount of processing solution decreases, resultant enrichment of processing solution concentration due to evaporation-which conventionally has not been a significant problem becomes a significant problem.
In a main processing tank, evaporation of processing solution is prevented through employment of a lid having a sealing structure. However, in a sub-tank provided for filtering, heating, and circulating processing solution from the main processing tank, employing a lid of a sealing structure as in the case of the main processing tank is difficult. That is, although the surface area of processing solution in the sub-tank is relatively small, various mechanisms such as a filter mechanism, a heating mechanism, a sensor mechanism, and a switch mechanism are present in the solution or on the solution surface, and the lid is frequently opened for adjustment and inspection, thus rendering difficult employment of a lid of a sealing structure.
Further, in the sub-tank, processing solution tends to evaporate from its surface more than in the main processing tank due to heating by the heating mechanism and due to turbulence at the surface of processing solution caused by flow of the processing solution. Moreover, reaction with air occurs more easily on a moving liquid surface as compared with a still liquid surface, and degradation of the processing solution proceeds more quickly.